The objective of the research is to evaluate the efficacy of artificial tooth roots employing a porous high density polyethylene (PHDPE) surface coating as the attachment vehicle through which the dental implants can be anchored in alveolar bone. The tooth roots are evaluated as free standing anterior and posterior teeth, and as distal abutments for 3 unit bridges in experimental animals. Thirty-nine PHDPE tooth roots were evaluated as free standing posterior dental implants in 14 dogs. Implant times ranged from 4-20 months. Twenty-one implants were rated clinically acceptable on the basis of mobility less than or equal to 1/2 mm and minimal radiographic bone loss. The 18 unacceptable implants displayed mobility greater than 1/2 and radiographic bone loss of more than 1 mm. Pocket depth measurements could be correlated with bone loss evidence by radiography. No correlation could be made between the implant status and the amount of plaque accumulation, the gingival appearance, or the degree of bleeding around the neck of the implant. These clinical signs were unremarkable until advanced stages of failure. Evaluation of the PHDPE implants in dogs revealed 3 characteristic histological profiles. One tissue response, considered acceptable, included bone growth into the porosity of the implant with little fibrous tissue seen in the pores. A second histological profile displayed bone adaptation to the porous coatings, with a thin fibrous layer often interposed between the bone and the implant. Associated with this response was densely organized fibrous tissue with spindle shaped cells and occasional chronic inflammatory cell infiltrate extending into the porosity. This response was considered potentially problematic since the histological features observed could predispose the implant to failure with longer implantation time. A third tissue response included bone resorption along the coronal and apical aspects of the porosity, and excessive inflammatory cells and fibrous infiltrate completely involving the apical porosity. No difference in tissue response could be correlated with pore size of the PHDPE coating (125 or 250 micrometers average pore size).